<?php
class NextNodeNode
{
    public $next=null;
    public $first_sub=null;
    public $data=null;
    static public function create()
    {

    }
}

class NextNodeTree
{
    public $root=null;
}

class ParentNodeNode
{
    public $parent=null;
    static public function create()
    {

    }
}

class ParentNodeTree
{
    public $list=[];
}

class TreeNode
{
    public $parent=null;
    public $next=null;
    public $first_sub=null;
}

class Tree
{
    public $root=null;
    public $list=[];
}
